If you receive a call from an English speaking agent:
Try to identify their number and call "them" back whilst speaking: In this case, the "0211-95989538" number on our display was a nonlisted number .
They say they call you from Hong Kong via VOIP to offer you an investment bargain.
Try to let them talk as long as possible and do a trace root.
These guys are very clever and very well trained to hook you on.
Try to be as clever as they are... and even better :-)